> > I also have a similar observation for proteins purified by Ni-NTA column. > After concentrating the sample eluted from the Ni-NTA column, I see a > brownish-yellowish tinge closer to the bottom of the filter with colorless > buffer on top. This is observed even for non-metal binding and non-FeS > cluster proteins and also for proteins after removal of the His-Tag. This is > presumably arising due to difference in viscosity where the protein gets > concentrated closer to the bottom of the filter. > > > Or more likely: Nickel bleeding from the column was complexing bME or DTT in your sample: Ni-bME forms a tight brown complex.
Filip Van Petegem
